Various moving bin sorters have been developed wherein an array of horizontally extended trays are adapted to be sequentially opened at their inlet ends to enhance freedom of sheet entry into the bin space between trays.
Opening of the trays to provide such space may be as a result of movement of the trays by spiral cams, as in U.S. Pat. No. 4,343,463 and 4,911,424 or so-called geneva cams may move the trays as in U.S. Pat. No. 4,328,963, wherein the trays are moved upwardly or downwardly past the sheet inlet location. On the other hand, the trays may be separated at their sheet inlet ends by a cam which moves vertically from tray to tray and also moves the sheet infeed to the opened tray location as in U.S. Pat. No. 4,478,406.
The prior patents referred to above are merely representative of a substantial number of moving bin sorters in which a reversible electric motor drives the cams in opposite directions to sequentially open the trays to enhance sheet entry, and in the operation of which the motor force required to move the cams and thus to open the trays varies. The force required increases in proportion to the number of trays which must be displaced by the cams, the weight of the paper in the trays which are moved, the direction of movement and the extent to which the tray and paper weight may be counterbalanced by a spring, as shown in U.S. Pat. No. 4,328,963 or a comparable counterbalancing spring in other moving bin sorters, such as the sorter illustrated in U.S. patent application Ser. No. 016,450 filed Feb. 11, 1993, co-owned herewith and in U.S. Pat. No. 4,941,659.
The force applied to the trays to move them, therefore, is generally the maximum force necessary to move the maximum load composed of the maximum number of trays with the maximum number of sheets of paper of maximum weight, taking into account any counterbalancing force acting in an upward direction which must be overcome by motor force to move the trays downwardly below the cams when such trays are not loaded with paper sheets.
In practice, the use of motor force and speeds in excess of what is necessary or required to move the trays has historically caused the sorting machines to produce excessive noise and function when the workload is light. This is because the level of noise generated by the electric motor, the gearing which drives the tray shifting mechanisms, and the tray themselves, as well as friction loading and heat vary with load and speed.
Because office machine noise in an office environment can be objectionable and, in some cases, perhaps exceed the level permitted by regulation, efforts have been made to reduce the total noise level of sorting machines. For example, in U.S. Pat. No.5,193,801 the noise caused by the speed at which trays are moved in moving bin sorters can be reduced by varying the speed of the cam drive motor so that at the time of contact trays with one another the trays are moving at a low rate of speed, but during the major portion of the shifting movement of the trays they are moved at a high rate of speed regardless of the load. Also in U.S. patent application Ser. No. 016,450 referred to above and owned in common herewith, the power applied to a stapler in the sorter is varied depending upon the number of sheets to be stapled to reduce noise otherwise caused by applying the same force for stapling relatively few sheets as is required to staple the maximum number of sheets.